The long-term goal of the proposed research is to characterize intrarenal electrolyte metabolism. Several major factors have been studied including the determinants of glomerular filtration and the regulation of electrolyte excretion. The general objective of the proposed research is to tie together electrolyte transport metabolism with the regulation of glomerular filtration rate. The specific objective of the proposed research is to test the hypothesis that adenosine plays a role in the regulation of glomerular filtration rate. First, the effects of exogenous adenosine infusion will be characterized in regard to pre- and post-glomerular resistances and glomerular capillary ultrafiltration coefficient in the dog. In parallel we will test the hypothesis that the intrarenal effects of adenosine are mediated by angiotensin II. Next, we will evaluate the regulatory role of endogenous adenosine in two models involving changes in the filtered load of sodium, infusion of hypertonic saline solutions and reduced renal perfusion pressure. Since the renin-angiotensin and prostaglandin systems are involved in an interrelated fashion in the vasomotor responses, the individual and interactive roles of these systems in glomerular dynamics will be determined. These studies should form a firm foundation for the relationship between renal metabolism and the regulation of renal hemodynamics.